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A cast machine is usually used for metal die casting processes. This casting method uses mold cavities to apply high pressure to molten metal. In general, molds are machined from high-strength alloys, some of which are similar to injection molding. The bulk of die castings are made of non-ferrous metals such as zinc, copper , aluminum, magnesium, silver, tin and gold alloys and their alloys. Depending on the form of die casting, a cold chamber casting machine or a hot chamber casting machine is required. The key subject of this article is the manufacturing method of die casting. To order to give you a thorough understanding of the die casting process, we will introduce you to the basic two types of die casting machines and specific manufacturing processes.
Generally speaking, cast machines can be divided into two groups, hot chamber die casting machines and cold chamber die casting machines. The difference is how much force they can withstand. Typical pressure can be anywhere between 400 and 4,000 tons.
Hot chamber cast machine
Hot chamber cast machines are sometimes called gooseneck cast machines which relies on a pile of molten metal to fill the mold under pressure. At the beginning of the cycle, the piston of the machine is in a retracted state, at which time the molten metal will fill the "gooseneck". Pneumatic or hydraulic pistons squeeze the metal and fill it into the mold. A certain amount of molten metal is then moved to an unheated injection chamber or a nozzle. All metals are forced into the container through hydraulic or mechanical pressure. Due to the need to transfer the molten metal to the cold room, the long cycle time is the main downside of this operation. Cold chamber cast machines are also available in both vertical and horizontal models. Vertical die cast machines are usually small machines, whereas horizontal die casting machines are available in various sizes. Cold chamber casting machines are constructed in such a way that the casting set is put outside the melt.
Cold chamber cast machine
Cold die cast machines are be used for die casting metals that cannot be used in the hot chamber cast machines, including aluminum, magnesium, copper and zinc alloys with high aluminum content. In this process, first of all, the metal needs to be melted in a separate crucible. A certain amount of molten metal is then moved to an unheated injection chamber or to a nozzle. Both metals are inserted by hydraulic or mechanical pressure into the container. Due to the need to move the molten metal to the cold room, the long cycle time is the greatest drawback of this process. Cold chamber molding machines are also available in both vertical and horizontal models. Vertical die casting machines are typically small machines, whereas horizontal die casting machines are available in various sizes. Cold chamber casting machines are constructed in such a way that the casting collection is placed outside the melt.
The high-pressure die-casting process includes four steps, including mold preparation, filling, injection and shaking, which is also the basis of various improved die-casting processes. Check out the steps below to get a general idea of how to use a cast machine for die casting process.
During the preparation process, it is necessary to spray lubricant into the cavity. In addition to helping to control the temperature of the mold, the lubricant can also help remove the casting, and then the mold can be turned off.
The molten metal is filled into the mold at a high pressure of about 10 to 175 MPa. When filling molten metal, maintain pressure until the casting is solidified.
The next step is to open the mold in the cast machine and remove the top mold through the thimble. High-pressure injection will fill the mold very rapidly so that the molten metal will fill the whole mold until any component is solidified. Therefore, also in thin-walled sections that are difficult to fill, surface discontinuities can be avoided. Some die castings may be used to conduct tasks that cannot be finished by casting, such as drilling and polishing.
The shaking process requires separation of waste materials, including gates, runners, dirt and flash. This process is usually accomplished by extruding the casting through a special dressing die. Other sand dropping methods include sawing and grinding.
After the shaking process is completed, defects can be checked. The most common defects include stagnation and cold head.
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